1. Field of the Invention
The present invention relates to a thermoplastic elastomer hose having excellent flexibility.
2. Description of the Related Art
Rubber hoses in general comprise an inner tube, a reinforcing layer and an outer cover, and the inner tube and the outer cover are composed of a vulcanized rubber. However, such rubber hoses have disadvantages in that the production process is complicated and troublesome because they require a vulcanization process.
On the other hand, so-called "resin hoses" are known in the art. The resin hoses comprises inner tubes and outer covers composed of a thermoplastic resin and can be produced by a simple production process, in which a vulcanization process is not required. However, thermoplastic resins constituting such resin hoses are generally harder than a vulcanized rubber, and therefore, it has been difficult to obtain soft and flexible hoses.
To improve the flexibility of thermoplastic resins, a resin hose composed of a polyester thermoplastic elastomer using polybutylene terephthalate as a hard segment and polytetramethylene glycol or polycaprolactam as a soft segment for the inner tube is also known. However, there is a limitation to the reduction of the hardness of the polyester thermoplastic elastomer so as to secure the heat-resistance and to exhibit the strength characteristics. For this reason, hoses having sufficient flexibility comparable to that of rubber hoses have not yet been obtained.
Accordingly, there are needs in the development of hoses, which can be produced by a simple production process not requiring the vulcanization process, which have sufficient flexibility and moreover, which have sufficient heat-resistance to withstand application at a high temperature such as pressure transmission and fluid transportation.